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PubMed2022

Spatial-temporal and phylogenetic analyses of epidemiologic data to help understand the modes of transmission of endemic typhoid fever in Samoa.

Salmonella enterica serovar Typhi (S. Typhi) is either widely distributed or proximally transmitted via fecally-contaminated food or water to cause typhoid fever. In Samoa, where endemic typhoid fever has persisted over decades despite water quality and sanitation improvements, the local patterns of S. Typhi circulation remain unclear. From April 2018-June 2020, epidemiologic data and GPS coordinates were collected during household investigations of 260 acute cases of typhoid fever, and 27 asymptomatic shedders of S. Typhi were detected among household contacts. Spatial and temporal distributions of cases were examined using Average Nearest Neighbor and space-time hotspot analyses. In rural regions, infections occurred in sporadic, focal clusters contrasting with persistent, less clustered cases in the Apia Urban Area. Restrictions to population movement during nationwide lockdowns in 2019-2020 were associated with marked reductions of cases. Phylogenetic analyses of isolates with whole genome sequences (n = 186) revealed one dominant genotype 3.5.4 (n = 181/186) that contains three Samoa-exclusive sub-lineages: 3.5.4.1, 3.5.4.2, and 3.5.4.3. Variables of patient sex, age, and geographic region were examined by phylogenetic groupings, and significant differences (p<0.05) associated genetically-similar isolates in urban areas with working ages (20-49 year olds), and in rural areas with age groups typically at home (<5, 50+). Isolates from asymptomatic shedders were among all three sub-lineages. Whole genome sequencing provided evidence of bacterial genetic similarity, which corroborated 10/12 putative epidemiologic linkages among cases and asymptomatic shedders, as well as 3/3 repeat positives (presumed relapses), with a median of one single nucleotide polymorphism difference. These findings highlight various patterns of typhoid transmission in Samoa that differ between urban and rural regions as well as genomic subtypes. Asymptomatic shedders, detectable only through household investigations, are likely an important reservoir and mobile agent of infection. This study advances a "Samoan S. Typhi framework" that supports current and future typhoid surveillance and control efforts in Samoa.

Humans↗
PubMed1986

Risk factors for malnutrition in Brazilian children: the role of social and environmental variables.

The article reports the effects of several socioeconomic and environmental indicators on the nutritional status (stunting, underweight, and wasting) of a sample of 802 children aged 12-35.9 months in urban and rural areas of southern Brazil. Of the social variables studied, family income and father's education level were the two risk factors that showed the strongest associations with nutritional status. The mother's education level, employment status of the head of the family, number of siblings, and family's ethnic background also showed some degree of association, but these were less significant when family income was included in the analysis. Environmental variables, particularly the type of housing, degree of crowding, and type of sewage disposal, were also strongly associated with malnutrition. The effects of having access to piped or treated water were only apparent on stunting and wasting.

Anthropometry↗
PubMed2004

Spatial distribution of polybrominated diphenyl ethers in southern Ontario as measured in indoor and outdoor window organic films.

Organic films were collected from indoor and outdoor window surfaces, along an urban-rural transect extending northward from Toronto, Ontario, Canada, and analyzed for 41 polybrominated diphenyl ether congeners (PBDE). For exterior films, urban sigmaPBDE concentrations were approximately 10x greater than rural concentrations, indicating an urban-rural gradient and greater PBDE sources in urban areas. Urban films ranged from 2.5 to 14.5 ng/m2 (mean = 9.0 ng/ m2), excluding the regional "hotspot" Electronics Recycling Facility, compared to 1.1 and 0.56 ng/m2 at the Suburban and Rural sites. Interior urban films (mean = 34.4 ng/m2) were 3 times greater than rural films (10.3 ng/m2) and were representative of variations in building characteristics. Indoor films were 1.5-20 times greater than outdoor films, consistent with indoor sources of PBDEs and enhanced degradation in outdoor films. Congener profiles were dominated by BDE-209 (51.1%), consistent with deca-BDE as the main source mixture, followed by congeners from the penta-BDE mixture (BDE-99:13.6% and -47:9.4%) and some octa-BDE (BDE-183:1.5%). Congener patterns suggest a degradative loss of lower brominated compounds in outdoor films versus indoor films. Gas-phase air concentrations were back-calculated from film concentrations using the film-air partition coefficient (K(FA)). Mean calculated air concentrations were 4.8 pg/m3 for outdoor and 42.1 pg/m3 for indoor urban sites, indicating that urban indoor air is a source of PBDEs to urban outdoor air and the outdoor regional environment.

Air Pollutants↗
PubMed2003

Effects of geographical location and land use on atmospheric deposition of nitrogen in the State of Connecticut.

A network of eight monitoring stations was established to study the atmospheric nitrogen concentration and deposition in the State of Connecticut. The stations were classified into urban, rural, coastal and inland categories to represent the geographical location and land use characteristics surrounding the monitoring sites. Nitrogen species including nitrate, ammonium, nitric acid vapor and organic nitrogen in the air and precipitation were collected, analyzed and used to infer nitrogen concentrations and dry and wet deposition flux densities for the sampling period from 1997 through 1999, with independently collected meteorological data. Statistical analyses were conducted to evaluate the spatial variations of atmospheric concentration and deposition fluxes of total nitrogen in Connecticut. A slightly higher atmospheric concentration of total nitrogen was observed along the Connecticut coastline of Long Island Sound compared to inland areas, while the differences of nitrogen deposition fluxes were insignificant between coastal and inland sites. The land use characteristics surrounding the monitoring sites had profound effects on the atmospheric nitrogen concentration and dry deposition flux. The ambient nitrogen concentration over the four urban sites was averaged 38.9% higher than that over the rural sites, resulting a 58.0% higher dry deposition flux in these sites compared to their rural counterparts. The local industrial activities and traffic emissions of nitrogen at urban areas had significant effects on the spatial distribution of atmospheric nitrogen concentration and dry deposition flux in the State. Wet and total deposition fluxes appeared to be invariant between the monitoring sites, except for high flux densities measured at Old Greenwich, a monitoring station near to and downwind of the New York and New Jersey industrial complexes.

Agriculture↗
PubMed2001

Clustering of childhood mortality in rural Burkina Faso.

BACKGROUND: Childhood mortality is a major public health problem in sub-Saharan Africa. For the implementation of efficient public health systems, knowledge of the spatial distribution of mortality is required. METHODS: Data from a demographic surveillance research project were analysed which comprised information obtained for about 30 000 individuals from 39 villages in northwest Burkina Faso (West Africa) in the period 1993--1998. Total childhood mortality rates were calculated and the geographical distribution of total childhood mortality was investigated. In addition, data from a cohort of 686 children sampled from 16/39 of the villages followed up during a randomized controlled trial in 1999 were also used to validate the results from the surveillance data. A spatial scan statistic was used to test for clusters of total childhood mortality in both space and time. RESULTS: Several statistically significant clusters of higher childhood mortality rates comprising different sets of villages were identified; one specific village was consistently identified in both study populations indicating non-random distribution of childhood mortality. Potential risk factors which were available in the database (ethnicity, religion, distance to nearest health centre) did not explain the spatial pattern. CONCLUSION: The findings indicate non-random clustering of total childhood mortality in the study area. The study may be regarded as a first step in prioritizing areas for follow-up public health efforts.

Burkina Faso↗
PubMed1976

Policies to influence the spatial distribution of physicians: a conceptual review of selected programs and empirical evidence.

To increase the usefulness of existing physician location literature for policy evaluation, literature is grouped into intraurban and urban-rural studies. A conceptual overview of physician location literature is presented. Consensus results, if any, are discussed. A list of hypotheses suggested by the literature is then utilized in a discussion of economic social, prior exposure, and professional development incentives embodied in selected public and private sector programs. Programs are evaluated by type of incentive mechanism and geographic target area to determine if present program structures are based on a solid empirical foundation. This assessment indicates that, in general, use of prevalent location incentive mechanisms is not justified by a consensus of empirical evidence.

Economics↗
PubMed1999

Biomedicine on the spatial periphery: the (re)production of a metaphorical landscape by rural health care practitioners in northern California.

I examine the use of spatial concepts by rural health care practitioners in Northern California and suggest that rural and urban spatial metaphors are important means of expressing and (re)producing problems associated with their search for legitimacy and moral authority within a field of relations defined by biomedicine. I present three broad ways in which spatial metaphors are used by rural health care practitioners to continuously enact a "metaphorical landscape." I situate this landscape in the context of a hierarchical field of relations within biomedicine, which is itself underpinned by a distinct urban bias and the uneven distribution of material and technological resources. I suggest that this landscape is partly the result of the rural health care practitioners' position within this field of relations and partly the result of implicit and historically situated frameworks of spatial meanings derived from capitalism.

Anthropology↗
PubMed1998

An investigation of environmental levels of cadmium and lead in airborne matter and surface soils within the locality of a municipal waste incinerator.

The results of an investigation into the environmental impact of heavy metals in the airborne emissions from the Baldovie municipal waste incinerator, Scotland, are presented. A sampling network of 1-km grid squares covering a 7 x 9 km area was established over the incinerator plant and its surroundings. Surface soil core samples were collected from within each 1 km2 and analysed for cadmium and lead content. The spatial distribution of lead levels in soils showed a marked variation downwind from the Baldovie incinerator in comparison with the background level for the area but remained well within the typical range of lead in rural, unpolluted, British soils. A comparison of the observed levels of lead in local soils, with the predicted downwind long-term ground level lead distribution in air indicates that atmospheric emissions of lead originating from the Baldovie incinerator directly determine concentrations of lead in soils within a radius of 5 km of the incinerator. An empirical relationship between the levels of lead in soils and the long-term levels in air was established. In the case of cadmium, the spatial distribution of the heavy metal showed neither a marked nor extensive contamination of the sampled area around the incinerator and remained within the typical range of cadmium levels in rural, unpolluted, British soils. The work concludes that atmospheric emissions of lead from the Baldovie incinerator significantly determines the local distribution of lead in soils within the immediate vicinity of the incinerator.

Air Pollutants↗
PubMed1994

Population change and migration in Britain since 1981: evidence for continuing deconcentration.

Recent trends in spatial distribution and internal migration in Britain are reviewed using small-area statistics from the 1981 and 1991 censuses. "The results indicate that the differentials in the population growth rate between metropolitan and nonmetropolitan Britain narrowed somewhat between the 1970s and the 1980s, but the negative relationship between urban status and population change remained very clear. Moreover, contrary to the experience of the U.S.A. and a number of European countries, in the mid-1980s Britain saw a resurgence of nonmetropolitan growth which had widespread impact across the country."

Demography↗
PubMed1997

Damp housing conditions and respiratory symptoms in primary school children.

There is evidence that indoor air pollution contributes to the development of respiratory symptoms. This study examined the relationships between dampness in houses and respiratory symptoms in 4,164 primary school children in the subtropical rural areas of the Kaohsiung region, Taiwan. Dampness in homes was assessed by questionnaires that reported 1) general dampness, 2) mold or mildew inside the home, or 3) flooding (appearance of standing water within the home, water damage, or leaks of water into the building). Evidence for upper and lower respiratory symptoms were also collected by questionnaires. Recorded symptoms included cough, wheezing, pneumonia, bronchitis, and asthma. Degrees of dampness were reported as 12.2%, 30.1%, and 43.4%, respectively by the parents or guardians of the study population. The prevalence of respiratory symptoms was consistently higher in homes with indications of dampness than in non-damp homes. After adjustments for potential confounders, selected respiratory symptoms among the childhood population were significantly higher in damp than non-damp homes, with the exception of pneumonia. We conclude that dampness in the home is a strong predictor of and risk factor for respiratory symptoms and constitutes a significant public health problem in subtropical area.

Child↗